The present invention relates to systems for inflating pneumatic tires and, in particular, to a system for automatically inflating a pneumatic tire to a pre-selected pressure.
Tire pressure critically affects how long a pneumatic tire lasts and the fuel economy and handling characteristics of the vehicle on which the tires are mounted. Tire pressure may change over time as a result of fluctuations in air temperature and through small leaks between the rim and hub of the tire or through the tire's valve. For this reason, tire pressure should be checked periodically and corrected either by inflation or deflation as may be necessary.
It is convenient to check tire pressure at the time the vehicle is being serviced or fueled. Service stations often have a source of compressed air for operating pneumatic tools and tires may be inflated using a hose from this source having the proper chuck for connecting to the tire's valve stem. Using such an unregulated source of air pressure, the tire pressure is corrected on a trial and error basis by inflating (or deflating) the tire and frequently removing the chuck from the valve stem to check progress with a hand-held pressure gauge.
This method requires some skill and an accurate hand pressure gauge and thus may require the assistance of service station personnel, distracting them from their other duties. To the extent that the use of the hand gauge encourages a person to be close to the inflating tire, the risk of injury from an exploding tire is increased.
Automated inflation devices are known which inflate a tire under the control of a mechanical or electrical pressure switch. Such devices that have found their way into common usage have proven to be inaccurate and have fallen into disfavor.
The difficulty of providing a low cost automatic inflation device arises from the high cost of rugged and accurate pressure metering devices, lack of knowledge by the automotive public as to the proper operation of such devices, and the significant problems of safety and reliability of a mechanism operating largely unattended by inexperienced individuals.